Thousands of Hungarians protested in Budapest on Monday against a law expected to be approved by parliament Tuesday that would ban the "promotion" or "portrayal" of homosexuality or sex reassignment surgery.
The bill would effectively ban educational programmes and publicity of LGBT groups, who have compared it to similar legislation in Russia.
Over 5,000 people rallied outside the Hungarian parliament in a demonstration which one of the organisers, Amnesty International, said "showed that many people in Hungary reject homophobia and transphobia and the government's attempt to spread hatred".
"Tomorrow, when MPs are casting their vote, they should remember that they are risking people's lives for their cruel political campaign," they said in a statement.
Most opposition parties said they will boycott the vote, but parliament -- dominated by Prime Minister Viktor Orban's ruling right-wing Fidesz party which drafted the law -- is expected to approve it.
The organisers said the law would "severely restrict" freedom of expression and children's rights.
Advertising by companies such as Coca-Cola, which campaigned for gay acceptance in Hungary in 2019, would be banned, as would books dramatising homosexuality.
A commercial television channel RTL Klub Hungary said that popular movies such as "Bridget Jones's Diary", "Harry Potter", and "Billy Elliot" could only be shown late at night with an 18-plus classification.
It is the latest in a series of legislative measures in Hungary targeting paedophilia and aimed at protecting children and families.
Last December, parliament adopted a package of measures enshrining the traditional family, effectively banning adoption by same-sex couples.
"It is getting more and more uncomfortable to live here, not only for gays, but practically also for everybody," said a protester Attila Kelemen, 23, who works as a school psychologist.
"This kind of relentless propaganda which is blinding people is a bit extreme. And to mix up homosexuality with sexual crimes is disgusting," he told AFP.